1. Field of the Invention
The present invention relates generally to stabilizing and cementing lateral well bores, and more particularly, to stabilizing lateral well bores whereby erosion and deformation which adversely affect subsequent primary cementing operations are prevented.
2. Description of the Prior Art
In multi-lateral wells, the lateral well bores are drilled and extend from a single primary well bore. The primary well bore can be substantially vertical or deviated and it can have a plurality of lateral well bores extending therefrom in various directions at the same or different depths. Casing is usually run in the primary well bore and cemented therein prior to the drilling of lateral well bores therefrom. The lateral well bores are typically drilled by sealingly positioning a whipstock in the primary well bore and milling or otherwise forming an opening through the primary well casing and cement. A lateral well bore is then drilled through the opening to a desired length. Thereafter, casing, also referred to as a liner, is usually run into the lateral well bore and cemented therein.
In the cementing of a liner in a lateral well bore, it is mandatory that an effective seal is formed at the junction of the lateral well bore liner to the primary well bore casing. The success in forming such a seal is directly related to the ability to accurately displace a cement slurry into the junction location during the cementing of the liner. However, the open-hole portion of the lateral well bore adjacent to and extending a distance from the junction (primarily the curved portion) is exposed to both erosional and mechanical deformation stresses throughout the lateral well bore drilling process which have the affects of enlarging that portion of the lateral well bore. Further, additional erosional and mechanical stresses are applied to the walls of the lateral well bore when casing is run into the well bore and drilling fluid is circulated through the annulus between the casing and the walls of the well bore. The combined effect of such mechanical and erosional stresses is that the portion of the lateral well bore adjacent its junction with the primary well bore is enlarged, sometimes greatly, as compared to its normal expected size. The enlarged portion of the lateral well bore prevents the predicted quantity of cement slurry displaced into the annulus between a liner and the walls of the well bore during primary cementing from reaching the junction of the lateral well bore with the primary well bore and consequently a seal at the junction does not result.
Thus, there is a need for methods of stabilizing a lateral well bore at its junction with a primary well bore to prevent erosion and deformation and to allow an effective seal at the junction to be formed when a liner is cemented in the lateral well bore.